Soluble oil compositions for metal working



United States Patent F 3,365,397 SOLUBLE OIL COMPOSITIONS FOR METAL WORKING Ivan S. Kolarik, Wyckolf, N.J., assignor to Mobil Oil Corporation, a corporation of New York No Drawing. Continuation-impart of abandoned application Ser. No. 429,661, Feb. 1, 1965. This application Aug. 4, 1966, Ser. No. 570,152

9 Claims. (Cl. 25233.6)

' This invention relates to a method for improving lubricating oil compositions and in particular it relates to a novel method for extending the service life of lubricating oil emulsions used in metal working. This application is a continuation-in-part of US. patent application Ser. No. 429, 661, filed on Feb. 1, 1965, and now abandoned.

In the rolling of non-ferrous metals, such as aluminum, billets of the metal are passed through steel rollers which compress the metal-into sheets and strips of a particular gauge. Soluble roll oils, usually applied in the form of oil-in-water emulsions, are used both to lubricate the rollers as the metal passes through and to facilitate entry of the billet into the bite of the rollers. By coating the rollers with the emulsion, welding is also prevented. (Welding is an adhesion between the steel and aluminum and results in a marred surface on the finished aluminum sheet.) Another function of the oil is to capture and remove metal fines occasioned by the rollingoperation and dirt and other impurities which may mar the surface of the metal.

In the past, the service life of the emulsion has not been extensive, replacements usually made in from about three to nine months. However, with the increased use of the newer and more pliable aluminum alloy products, even after as short a time as five or six weeks of service, roll oil batches have had to be completely replaced because the V emulsions have broken down and separation of phases has resulted. Moreover, much of the emulsion is lost in daily skimmings, which are portions of the emulsion in which the entrapped solid impurities are concentrated after a settling period. These portions generally rise as an upper layer above the oil emulsion enabling them to be skimmed off periodically. Small additional portions of emulsion are added to make up the loss. The loss of oil in the skimmings, however, is very considerable, and increased make-up additions to replace the continual loss of emulsion are required.

It is an object of this invention to provide a method of extending the life of a used roll oil emulsion. Another object is to provide a method of preventing the demulsifying effects of roll oil emulsions used in metal rolling operations. This and other objects will become apparent from the following disclosure.

It has now been discovered that the life of a used oilin-water emulsion lubricant for the rolling of metals, wherein the lubricant is susceptible to emulsion breakdown by the accumulation of polyvalent metal ions dissolved therein, may be extended by the steps of:

(1) Using the emulsion as a lubricant in normal metal rolling operations and mechanically removing from said emulsion after each metal rolling operation solid metal particles and separated oil;

(2) Permitting the concentration of dissolved polyvalent metal ions in the said remaining used emulsion to rise with each rolling operation until it reaches a level at which emulsion breakdown tends to occur; and

(3) Adding to the said remaining used emulsion a sequestering agent capable of resisting the metal-ion induced breakdown of said emulsion, wherein the said metal ion is magnesium, aluminum, iron or calcium.

Surprisingly the agents used in this invention are extremely effective in maintaining the oil-in-water emulsion 3,365,397 Patented Jan. 23, 1968 ICC during use, even though they are used in relatively minute amounts.

While it has heretofore been postulated that the breaking down of the soluble oil emulsion had been caused by the introduction of foreign matter found in the rolling equipment, such as grit, dirt, and even bacteria, the safeguards hitherto used against these impurities have had little effect. It has been discovered that the working of high-magnesium aluminum alloys introduces an excessive amount of magnesium ions into the roll oil emulsion. I believe that the higher reactivity of magnesium in comparison with the other typical polyvalent ions to be found in the oil emulsion, viZ., copper, iron, and calcium, creates an unstable condition. Surprisingly, I find that the oil emulsions have a lower tolerance for the magnesium than for the other above-noted impurities. It was not expected that metal ions would attack the discrete droplets or particles, of the dispersed oil in the water and thus destroy the emulsion, since in the past this breakdown had been very gradual and the service life of the oil emulsion had been comparatively extensive.

In evaluating the destructive effect of the magnesium ions upon the oil emulsions, analyses were made of the daily skimmings in a typical aluminum rolling mill. As defined earlier, skimmings are the waste emulsions usually discarded after each day of operation. Reasonably enough, these skimmings contained large amounts of aluminum, iron and magnesium, present as fine particles. The aluminum and iron were found to be in great abundance compared to the magnesium concentration. However, surprisingly the remaining emulsion from which these skimmings were taken contained a far greater amount of magnesium ions than iron and aluminum ions together. I therefore conclude that the magnesium ions which cannot be extracted from the emulsion contribute most singularly to the destruction of the emulsion.

Moreover, considering the large quantity of magnesium ions with which the oil emulsions come in contact, it was unexpected to find that the addition of the sequestering agent of this invention in such small amounts could successfully overcome the specific deteriorative characteris tics of these ions.

A typical soluble oil composition, termed neat oil, usually consists of the lubricating oil, such as a solventrefined paraffinic or naphthenic oil, an emulsifying agent, preferably an anionic soap, such as fatty acid-alkanolamine reaction product, and special additives, including a bactericide, such as phenol, which impart desirable properties to the emulsion. The neat oil composition is mixed with sufiicient water to provide an emulsion which contains by volume about 90% to 97% water and 10% to 3% by volume of the oil formulation. The ingredients of the neat oil usually are present in the following general proportions by volume.

Material: Percent by volume Lubricating oil 70 to Emulsifier (anionic soap) 10 to 25 Bactericide (phenol) Oto 1.0

The sequestering agent is added to the oil-in-water emuland ascorbic acid. Another class of suitable sequestering agents includes those of the general classification of Schiff bases. Of particular interest are those prepared from hydroxyaromatic aldehydes or ketones, such as salicylaldehyde or o-hydroxyacetophenone, reacted with polyarnines, such as ethylenediamine or propylenediamine; for example, N,N-disalicylidine (ethylenediamine). Another group which may be used are the diketones, such as RCOCH COCF wherein R is an alkyl group of from 1 to about 4 carbon atoms; among these may be used 1,1,l-trifiuoro-2,4-pentanedione.

These additives may be present in the emulsion at a concentration of from about 0.5% to about 15% by weight of the oil phase. The most preferred of the sequestering agents according to this invention are ethylenediaminetetraacetic acid and ethylenediaminetetraacetic acid tetrasodium. It is completely unexpected to find that the addition of such small amounts of the additives to a roll oil emulsion formulation may extend the service life of the emulsion to as much as from six to nine months or longer, regardless of the type of aluminum alloy being worked, whereas in the absence of these additives the emulsion could break down in as short a time as three weeks. Moreover, I find that the addition must be made 947 by volume of water and 6% by volume of the soluble oil mixture. These emulsions were obtained by adding the oil mixture at a temperature of about 80 F. to distilled water held at a temperature in a range of 100 to 110 F. As the oil was added, the water was vigorously agitated.

To 100 ml. samples of these emulsions were added standard solutions of magnesium chloride, aluminum chloride, ferric chloride and calcium chloride. These standard solutions are deemed to simulate polyvalent ions found in oil emulsions in use in the rolling mills. The amounts of the stock solutions added were varied to obtain different concentrations of cations. Several concentrations tested were, of course, far in excess of the normal concentrations found in actual practice. Each sample was shaken vigorously after the addition of the stock solution and was placed in a 150 F. oven for 72 hours. An identical set of samples were held at room temperature (RT). These samples were examined periodically during the 72 hour test. In rating the sample for degree of separation of the oil from the water (indicating a breakdown of the emulsion) the description indicates less than /6 by volume of oil separated and 6 indicates complete separation of the oil. The ratings between 0 and 6 are approximations of the percent volume of oil separated.

TABLE 1 2 hrs. 24 hrs. 48 hrs. 72 hrs. Metal Ions, p.p.rn.

RT 150 F. RT 150 F. RT 150 F. RT 150 F.

1. Calcium:

after the emulsion has already been in use to receive optimum etfect. By adding the sequestering agents of this invention in the amounts indicated to the working emulsion, maximum extension of the service life is obtained and the tendency for welding of the metal is reduced.

The addition to the emulsion of the sequestering agent, preferably the ethylenediaminetetraacetic acid or its alkali metal salt, appears to have the effect of complexing the dissolved metallic particles into non-destructive molecules. The attack by the polyvalent ions, particularly by the magnesium, upon the dispersed oil particles or upon the emulsion balance, is thus theorized as being substantially lessened.

COMPARATIVE EXAMPLES Example I .T est of standard oil emulsion The typical roll oil formulation described heretofore was mixed with water to provide an emulsion containing Table I indicates that under 150 F. conditions, the emulsion had a tolerance of only 50 ppm. of magnesium ions after a 24 hour period, since by that time, over /6 of the oil had demulsified. Although at p.p.m. of aluminum, the emulsion breakdown is high, however, as discussed heretofore, most of the aluminum impurities are removed in the skimmings. The quantity of aluminum ions remaining in the emulsion after the skimmings are removed is much less than the magnesium ions, and hence does not present as great a threat to the emulsion stability as do the magnesium ions.

To illustrate, analytical tests for metal content were run on samples of an oil emulsion being used in the rolling of aluminum, to determine the quantity of magnesium, iron and aluminum. Both skimmings and emulsions were analyzed at various times during less than two months of use. During this time, about half of the aluminum rolled was the high-magnesium aluminum alloy.

This aluminum alloy contained less than by weight of magnesium metal. The results are given in Table II, in parts per million of metal (either as ions or fines) and percent of the three metals. The samples are numbered according to chronological order, each sample being taken from 3 days to 2 weeks after the preceding sample.

6 described 'hereinabove, such as emulsifiers, bactericides, load-carrying agents, and the like.

Although the present invention has been described herein in terms of specific embodiments and examples thereof, it is not intended that the scope thereof be limited in any way thereby except as indicated in the following claims.

TABLE II Skimmings Emulsion Time Sample Elapsed After Last Mg Fe Al Mg Fe A1 Sample P.p.m Percent P.p.m Percent P.p.m Percent P.p.m Percent P.p.m Percent P.p.m Percent .5 14.1 31.8 .5 10. 4 37. 4 1, 370 52. 2 9 days- 640 20. 4 878 28.1 1, 610 51. 5 54 55. a 22 22. 7 21 21. 7 3 days. 647 14. 7 1, 242 28.2 2, 510 57.1 30 4s. 4 24. 2 17 27. 4

As may be concluded from the above table, the I claim:

discarded skimmings contain a high percent of aluminum and iron and a low percent of magnesium, i.e., no greater than about 20% of the three metals. However, the magnesium concentration in the remaining emulsion is considerably higher than the other two metals. The magnesium content increases during service, until it reaches a level above the point of initial emulsion breakdown, 50 ppm, while the levels of the other two metals remain well within the safe limit.

Example Il.Test of oil emulsions containing additive Amount of Additive, Percent by Weight of Oil Magnesium Ion, ppm.

COO

The results shown in the above table indicate that the exceedingly small addition of additive tends to increase the tolerance of the oil emulsion to the magnesium ion. In some cases I find that the magnesium-ion tolerance is improved tenfold, although it may be noted that separation of the emulsion occurs at the extremely higher concentrations of the magnesium ion, in which case further additions of the additives of this invention may adversely affect the surface quality of the aluminum being rolled. The addition of the very small amounts of my additives, however, is singularly eifective. The life of the roll oil emulsion is so prolonged by the addition of such small amounts as to be completely unexpected.

I find that one or a combination of sequestering agents may be employed in the soluble oil. The additions may be made either to the neat oil, i.e., the oil mixture prior to emulsification, or to the finished oil emulsion at any stage during the service life. I also find that these additives are compatible with the other typical roll oil additives 1. The method of extending the life of a used oil-inwater emulsion lubricant for the rolling of metals, said emulsion being normally susceptible to emulsion breakdown by the accumulation of polyvalent metal ions derived from the said metal being rolled which are dissolved in the emulsion, comprising the steps of:

(1) using the emulsion consisting essentially of at least by volume of water, said water normally containing less polyvalent metal ions dissolved therein than is sufiicient to cause emulsion breakdown and up to 10% by volume of an emulsifiable mineral oil as a lubricant in normal metal rolling operations and mechanically removing from said emulsion after each metal rolling operation the solid metal particles and separated oil;

(2) permitting the concentration of dissolved polyvalent metal ions in the said remaining used emulsion to rise with each rolling operation until it reaches a level at which emulsion breakdown tends to occur; and

(3) adding to the said remaining used emulsion a sequestering agent capable of resisting the metal ioninduced breakdown of said emulsion, wherein the said metal ion is selected from the group consisting of magnesium, aluminum, and iron, the metal of said ion being present in the metal being rolled.

2. The method of claim 1 wherein the sequestering agent is selected from the group consisting of aminocarboxylic acids, alkali metal salts of aminocarboxylic acids, hydroxycarboxylic acids, diketones having from 5 to 9 carbon atoms, and hydroxyaromatic-Schiflf bases.

3. The method of claim 1 wherein the sequestering agent is selected from the group consisting of an aminocarboxylic acid and an alkali metal salt thereof.

4. The method of claim 3 wherein the alkali metal salt is ethylene-diaminetetraacetic acid tetrasodium.

5. The method of claim 1 wherein the addition is made at a metal ion concentration of about 50 parts per million.

6. The method of claim 1 wherein the sequestering agent is present in the emulsion at a concentration of from about 0.5% to about 15% by weight of oil.

7. The method of claim 6 wherein the rolled metal is a high-magnesium aluminum alloy.

8. The method of claim 1 wherein the emulsion contains from about 90% to about 97% by volume of water.

9. The method of claim 5 wherein the metal ion is magnesium.

FOREIGN PATENTS 582,237 9/1959 Canada.

References Cited UNITED STATES PATENTS OTHER REFERENCES B i d 252 312 X 5 Practical Emulsions, by H. Bennett, Chemical Publish- P i et 1, 252 312 X ing Co., Inc., Brooklyn, N. Y., 1943, p. 72.

Bersworth 25233.6

cafcas 252 33 6 DANIEL E. WYMAN, Primary Examiner.

Rudrich 252-335 10 C. F. DEES, Assistant Examiner.

Heiman 25233.6 

1. THE METHOD OF EXTENDING THE LIFE OF A USED OIL-INWATER EMULSION LUBRICANT FOR THE ROLLING OF METALS, SAID EMULSION BEING NORMALLY SUSCEPTIBLE TO EMULSION BREAKDOWN BY THE ACCUMULATION OF POLYVALENT METAL IONS DERIVED FROM THE SAID METAL BEING ROLLED WHICH ARE DISSOLVED IN THE EMULSION, COMPRISING THE STEPS OF: (1) USING THE EMULSION CONSISTING ESSENTIALLY OF AT LEAST 90% BY VOLUME POLYVALENT METAL, SAID WATER NORMALLY CONTAINING LESS POLYVALENT METAL IONS DISSOLVED THEREIN THAN IS SUFFICIENT TO CAUSE EMULSION BREAKDOWN AND UP TO 10% BY VOLUME OF AN EMULSIFIABLE MINERAL OIL AS A LUBRICANT IN NORMAL METAL ROLLING OPERATIONS AND MECHANICALLY REMOVING FROM SAID EMULSION AFTER EACH METAL ROLLING OPERATION THE SOLID METAL PARTICLES AND SEPARATED OIL; (2) PERMITTING THE CONCENTRATION OF DISSOLVED POLYVALENT METAL IONS IN THE SAID REMAINING USE EMULSION TO RISE WITH EACH ROLLING OPERATION UNTIL IT REACHES A LEVEL AT WHICH EMULSION BREAKDOWN TENDS TO OCCUR; AND (3) ADDING TO THE SAID REMAINING USED EMULSION A SEQUESTERING AGENT CAPABLE OF RESISTING THE METAL IONINDUCED BREAKDOWN OF SAID EMULSION, WHEREIN THE SAID METAL ION IS SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM, ALUMINUM, AND IRON, THE METAL OF SAID ION BEING PRESENT IN THE METAL BEING ROLLED.
 2. THE METHOD OF CLAIM 1 WHEREIN THE SEQUESTERING AGENT IS SELECTED FROM THE GROUP CONSISTING OF AMINOCARBOXYLIC ACIDS, ALKALI METAL SALTS OF AMINOCARBOXYLIC ACIDS, HYDROXYCARBOXYLIC ACIDS, DIKETONES HAVING FROM 5 TO 9 CARBON ATOMS, AND HYDROXYAROMATIC-SCHIFF BASES. 